% Derivative of Bessel function of the first kind.
%
%  z = besseljd(n,x) returns the derivative of the Bessel function of the
%  first kind of order n evaluated at points x. It is assumed that n is an
%  integer.
%
% Stuart C. Hawkins - 13 January 2015

function val=besseljd(n,x)

% compute values using formula derived from (9.1.30) in Abramowitz and
% Stegun, Handboook of Mathematical functions.
val = besselj(n-1,x) - n.*besselj(n,x)./x;

% ensure the result is a column vector
val=val(:);